to - dtic · part of npg research project apl-1. • object the investigation described in this...
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Distribution authorized to U.S. Gov't. agenciesand their contractors;Administrative/Operational Use; 29 JUL 1944.Other requests shall be referred to NavalProving Ground, Dahlgren, VA.
NSWC ltr 9 Sep 1976 ; NSWC ltr 9 Sep 1976
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NAr/O. PBOVINO GHOUTO DAHUJREN, VI8GINIA
s^>*
REPORT NO. 19-44
// J
VliS¥
Ä«i03 HU
PENETRATION OJ HOMOGENEOUS PLATE BY 3« 13.0 IB. FLAT NOSSD PROJECTILES FITTED
WITH WINDSHIELDS SECOND PARTIAL REPORT
ri DS a
29 Juiy 1944 0X
FIDENTiAl
NAVAL PROVING GROÜHD DAHLGHSE, VIRGINIA
HÄPORT NO. 19-U
PINSTRATION OF IIÜMOGSNBOUS PLATE BY 1« 13^0 LB. FLAT-NOSED PROJECTILES FITTED
WITH WINDSHIELDS SECOND PARTIAL REPORT
APPROVED:
DAVID 17 HEDRICK CAPTAIN, USN, COMMANDING OFFICER
PreTlous ReportSJ _^ , u (s%yo
I* 253 Report No. 7-43 dated 19 April 1943. i 2. NPQ Report No. 12-44 dated 20 April 1944. ^ ^ ^O Do \
Page i
PREFACE
AUTHORIZATION
This study was authorized in the Bureau of Ordnance letter NP9/A9(Re3) dated 9 January 1943, as part of NPG Research Project APL-1. •
OBJECT
The investigation described in this report was carried out for the purpose of comparing the performance of 3" fl-it-nosed and current armor pierc- ing projectilos in the attack of homogeneous plate.
SUMMARY
In previous experimental tests of flat-nosed projectiles (referonoes (1) and (2)) the projectiles used were monoblook and were not fitted with wind- shields. Since for the usual service applications windshields are essential, it was necessary to test the effect ot a windshield on tha penetration of homo- geneous plate by flat-nosed projectiles. Accordingly such projectiles were manufactured by Crucible Steel Company and tested at the Naval Proving Ground, The ballistic limits (minimum velocity required for pro- jectiles to pass completely through plate) obtained were compared with limits for 3-inoh M79 and 3-inoh Mk. 29-2 projectiles under the same test conditions.
The limit velocities for the flat-nosed projectiles were in general lower than were required by either 3-inoh Mk, 29-2 projectiles fitted with caps and windahl^lds or 3-inoh monoblock M79 projec- tiles. The advantage of the present flat-nosed pro- jectiles over other types of projectiles holds only for the attack of homogeneous plate (STS and Class B)
Page 11
up to e/d (Patio of plate tliiokness to projectile caliber) oi" 0.65 at most. The advantage is partic- ularly raarJced in the attack of divided armor and of thin plate (e/d of 0.5 or less) at high obliquities (45o-60o), When e/d is greater than O.65 the pro- jectiles are badly deformed or shattered on impact.
The results of the present tests together with previous results for flat-nosed projectiles are summarized in the following table. The limits are expressed as percentages of limits for undeformed 3" M79 projectiles under the same teat conditions.
Limit {j of M79 value) mi -feain
Windshield Flat-Nosed e/d Obliquity Mk. 29-2 (Flat-NosedKRef.(!)&(2))
0.16 0° 116 1U 102 30°,45°,60° 100-119 66-85 ^69 (45°)
0.36 0° 104 90 ^ — 30°,45°,60° 113-122 80-93
0.49 0° 117 88 62 30°,45°,60° 120-127 93-110 62-72
0.66 0° 125 97 62 30° 124 102 93 45° 133 126 101(40°)
From the above it is apparent that for e/d values up to 0.5 and obliquities up to 60° the pene- tration of homogeneous plate was accomplished by the flat-nosed projectiles at velocities on the average about 15^ below those required by monoblook and capped AP projectiles.
Against a divided structure consisting of 0','5 and 1M STS separated six (6) feet apart, the limit velocity for the flat-nosed projectile was 67^ of the Mk. 29-2 limit. The Mk. 29-2 projectile in all cases struck the second plate with about 45* yaw, whereas the flat-nosed projectile struck with 0° yaw. This difference in yaw together with the lower limit for the flat-nosed projectile accounts for the large observed difference in limit.
Page ill
■MKaa
in the at Jok oKonozensaL^ ^T^sei projectile ure to penetrate at M^ f^ ^mor lles iQ ^^ ™1~ their tendency to shatfL7 fecfuse of shatter and Mgh str^lnfveiocltiel ^^ tilinner ^ate at
projectiles fhl^ered Ind ffl?^aflnSt 2V5 STS the
above e/d of O^ö the nSsef ofe?H«0^e?etrQte' and
tiles were broken af high mfoltv lloaTT*, PT0^C' while they stood up at tLli^XS^^0^
emphasize ^hat^n^he attack ST** invest^atlon to e/d of 0.5 and at striwL f ^fSf**™* Plate up sec. flat-nosed prolect^«?! velocities below 2000 ft./ at velocities lol^oS^hf!0011.?11009331,111^ Penetrate of the current types AJÄ !?0f? re<luired by «my flat-nosed Drolect??: ay
ainat äiviäed structures the advantaglousf Jien view ^^f ^ be ^^icularly cation of th^ flatlnoLfl ni?S fb?ve» the ^rvice appli- offers ProiniL ofsSccfssPwi?h fL^«r?CketS and ^mbs
penetration efficiency 8 inorease in
.. i
Page iv
a«
oowrpra Page
I. IKTRODUCTION 1
II. MATERIAL AND METHODS I
J. v • ii «Low Uoö JL WJÜ «••«•«••e(«f«(t«(«tit«««**«* «♦
V« CONCLUSXONS*••.•*«••«•*•••«•••*••<«««« /
VIIe APPENDIX. 8
Pago T
LIST OF F.IGQRES
Opposite Page
Pigure 1 NPO Photo No. 1566 (API) View of 3" M79, 3W Mk. 29-2 and 3" Mk. 29 Flat-Nosed Projectiles.
Figure 2 NPG Photo No. 1751 (APL). Dependence of Fie/d,©) on Obliquity. 3W Mk. 29-2, 13.0 lb. Flat-Nosed, and 15.0 lb. M79 Projectiles vs. 0V5 ST3 at 0o-60o Obliquity.
Figure 3 NPG Photo No. 1658 (APL), View of Windshields and Projectiles after Penetrating 0«5 Plate at 30° and 45° Obliquity. 3" Mk. 29-2 and Flat-Nosed Projectiles.
Figure 4 NPG Photo No. 1640 (APL)9 View of Windshields and Projectiles after Penetrating Oi'i» Plate at 60° Obliquity. 3" Mk. 29-2 and Flat-Nosed Projectiles.
Figure 5 NPG Photo No. 1650 (APL). 075 STS vs. 3" Mk. 29-2 and Flat- Nosed Projectiles at Various Obliquities. Front View.
Figure 6 NPG Photo No. 1651 (APL), 0V5 STS va. 3n Mk. 29-2 and Flat- Nosed Projectiles at Various Obliquities. Back View.
Figure 7 NPG Photo No, 1752 (APL). Dependence of Fie/d,0) on Obliquity. 3W Mk. 29-2, 13.0 lb, Flat-Nosed and 15.0 lb. M79 Projectiles vs. 171 ST3 at 0°- 60° Obliquity,
Page vi
-X-W-
LIST OF FIGUBBa CONT'D
Opposite Page
Figure 8 NPO Photo No. 1753 (APL), Dependeiioe of F(8/d,@) on Obliquity. 1* Mk. 29-2, 13.0 lb. Flat-Nosed and 15.0 lb. M79 Projectiles ve. 1?5 STS at 0o-60o Obliquity.
Figure 9 NPQ Photo No. 1754 (APL). Dependence of F(e/d,9) on Obliquity. 3* Mk. 29-2,13.0 lb. Flat-Nosed, and 15.0 lb. M79 Projectiles at 0o-45o Obliquity.
Figure 10 NPG Photo No. 1510 (APL). 2.5 STS vs. Flat-Nosod Projectile at 0° Obliquity, Front View.
Figure 11 NPG Photo No. 1726 (APL). 3" Mk, 29-2 and 13.0 lb. Flat-Nosed Projsstllss va. Divided Structure (0V5 and 1VI STS Spaced 6 Feet Apart)
Page Tii
I. INTRODUCTION
In the past two years various experimental tests of flat-nosed projectiles have been carried out at 3-inoh scale at the Naval Proving Ground (references (1) and (2)). These tests showed that under certain conditions a flat-nosed projectile could penetrate homogeneous plats at 50^ of the velocity required by current projectile types. Particularly favorable results were observed against plates at high obliquity or against divided structures. The principal limita- tion of this type of projectile was found to be its inability to penetrate thick plate because of shatter. Thus its use was limited to the attack of str'i^tures with thicknesses not much greater than 1/2 osliber (e/d of 0.5). For this reason it was concluded that the principal possible application of the flat-nosed principal lay in bombs or perhaps special common pro- jectiles for the attack of lightly armored targets. As none of the projectiles used in these tests were fitted with windshields and since the usual service applications would necessarily require a windshield it was desirable to obtain for test flat-nosed pro- jectiles fitted with windshields. Crucible Steel Corporation was accordingly requested by the Bureau of Ordnance to manufacture 13.0 lb. flat-nosed projectiles fitted with windshields. The performance of these projectiles is discussed in the present report.
II. MATBRIAL AND METHCD3
Plate;
0V5 STS Carnegie-Illinois No. 0V5 STS Carnegie-Illinois No, 1V1 STS Carnegie-Illinois No. 1V5 STS Carnegie-Illinois No. 2?0 STS Carnegie-Illinois No. 3*0 Glass B Carnegie-Illinois 3V2 Class B Carnegie-Illinois
23115-A 612068 174140 40917 n790 No. 85187 No, X9021
(All plates are accepted STS and Class B plates.)
-1-
-•
.■;' ■ ■-■■ ■ ■■■ : .
NPG PHOTO NO. 1566 (APL) - CONFIDSNTIAL -
10 April 1944 FIGIiRE 3-
3" M79 .rvioi :k)
3' 1^29-2 (Assemt ■ d
3" Mk . ■ ,:■'■:■-
3" Mk : '* I loi '■■■ ■ ■
, i, ■■•) F lat-Mose H^scrv eml ■ :
., i
., ,, <
■ .; . :.-. .■ "*
■ -•■ ■ ■ ■ - •--
Projectiles;
Crucible Steel Co. 13.0-lb, 3" Mk. 29 Flat-nosed projectile (Buord Dwg. No. 124181) fitted with a steel wind- shield (0.21 lbs,)
Oldamoblle 13.0-lb. 3" Mk. 29-2 AP pro- jectile (Buord Dwg. No. 330770) fitted with cap and steel windshield (0,43 lbs.) Lot 81.
Frankford Arsenal 15-lb. 3" M79 AP shot. This projectile is a monoblook type with neither cap nor windshield.
Methods of Measurement
All ballistic limits reported herein are expressed in terms of F(e/d,9) values, where F(e/dle) is defined as follows;
F(e/d,e) ■ 41.57 M1^ Cos 9
77*1 M is the projectile mass In pounds, VT is the limit velocity in feet per second {tin minimum velocity required for a projectile to pass completely through the plate), 9, the obliquity, is the angle between the normal to the plate and tha line of flight, e is the plate thick« ness in inchr.s at the point of imoact, and d is the projectile diameter in inches. All of the quantities entering into the defining expression above are measured directly except the limit velocity. The limit velocity for any test condi- tion is calculated from the striking and residual velocities (references (1), (a) and (3)) or estiaated from the depth of penetration. For most of the test conditions both complete and incomplete penetrations were obtained to give a bracket of the limit. The residual velocity for the complete penetration and the depth of penetra- tion for the incomplete penetration are used t determine the value of the limit velocity within the bracket. As a measure of the amount of pro- jectile deformation the nameter of the forward bourrelet of each project.le was measured before and after each round. An/ gross deformations such as breakage were also noted.
-2-
Ill, RJSSOLTS
The results given in detail in the Appendix are suraiaarlzed below. F(e/d,©) values for 3" ISk. 29-2 and 3« Wk. 29 (flat-nosed) are given in columns 4 and I/ ^esPf^iyely. In parenthesis after each tabulated F(e/d,e} value are given the Fle/d,©) values as percentages of the standard 3" M79 limits {undeformed projectiles given by NPG Photo No. 1656 (APL) (reference UT).
SUMMABY OF BALLISTIC RESULTS
Observed Fie/d^)
Gauge e/d Obi. 3^ Mk. 2^-2 0Sf49 0,16 0°
30° 45° 60°
3" Mk. 29 (Flat-Nosed)
35,000±400 (116) 34,500±500 29,200±300 (107) 23,200±400 30,500±500 (119) 20,600±600 3O,50O±3OO (100) 19,900±300
Reference Plain
Flat-Nosed
(2)
U»08 0.36 0° 30° 45° 60°
1748 0.49 0° 30° 45° 60°
1798 0.66 0° 30° 45°
2743 0.81 0°
42,800±400 (104) 37,300±300 42,600±600 (115) 34,500±500 42,600±200 (122) 31,500±400 46,600±400 (113) 32,800±500
51,700±400 (117) 49,000±600 (123) 47,800±500 (127 $2,800±800 (120)
57,90O±30O (125) 51,90O±4O0 (124) 52,500±300 (133)
38,800±400 39,700±300 41,400±500 41,000±400
45,000±1000 42,600±400 44,600±400
114) 35,000±200 (102)* 85 ^ — 80)<23,600 ( 69)* 66) —
90) 93) 90) 80)
88) 28,500±200 ( 62 99) 30l100±300 ( 73
110) 32,600±200 ( 72) 93) 31,000±500 ( 62)
97) 28,600±500 ( 62) 102) 30,100±300 ( 93) 126) 32l600±200 (101)**
>48l200 0102) 41,000±1000( 86)
J^*
e/d of 0,20
40° obliquity
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nrnm 5 HPG PHOTO NO. 1650 (APL). APL Plate No. 394 (015 3T3 C.I.No. 23115-A) vs. 13.0 lb. 3" Olds. ISk. 29-2 AF projectiles and 12.90 lb. 3" 0.3. Co. Mk, 29 flat-nose AP projeotiles at 0°, 30° and 45° obliquity. FRONT VIEW. 3ee NPO Photo No. 1651 (APL) for baok view and data on impaots 2678-85 APL. B.I.No. *«" "0" 3 7..f. s. Proj. 1>
^71 APL 0,.,493 45o00' 5^9 Olds. 87 .';.\'i. " 44 ^O» 616 rt 94 2673 " 45"OO' 460 C.S.Co. 70 2674 m 44o50' 436 » 67 2675 " 45o00' 398 st 61 2676 01492 45o00, 427 n 65 2677 07493 45o10' 336 n 51 May 17s 18, 19, 1944
Pane. R.7. ,t,3. Inc.1/4"
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ProJ.Oor ^ off on tunnel.Proj, Iff on plate.
Whole,
- CONFIDENTIAL -
NPt5 PHOTO AFL Plate (AH,) for B.I.No.
2679 2680 2681 2682 2683 2684 2685 Kay 17, 18
NO. 1651 (API,). No. 394 (0^5 3T3 front view
"S." "6" S.V..f 0V493 30""00' -jjj 0';494 29° 50 0',,494 30° 00 0".U9k 30 "00 0^493 0o10 OV493 0°30' 0!493 CIO' OV493 0-30' . 19, 1944
.1. No, 23115-A) BACK 71W and data on impaota 2671-77 APL.
. 3 .
249 330 371 393 478 476 533
49 44 58 65 77 9J 93
104
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IV. DISCUSSION
In the evaluation of the performance of the 13oO lb. flat-nosed projectiles comparisons with standard armor piercing and common projectiles were considered desirable. Since the fiat-nosed projectiles were fitted with steel windshields, it was considered essential that one of the standard projectiles also have a steel windshield. Of the available projectiles the ones which best met this condition were service 3" Mk. 29-2 armor piercing projectiles, although these projectiles in addition to windshields are fitted with caps. The standard M79 projectile was used as a stan- dard common projectile since its performance against homogeneous plate is well known (references (3) and (4)). In the following the relative ballistic perfor- mances of the 3" flat-nosed projectile, the 3I, Mko 29-2, and 3" M79 are discussed.
At e/d of 0.16 the ballistic limits of the flat-nosed projectiles are lower than the correspond- ing 3" Mk. 29-2 and M79 limits at all except normal obliquity. (Figure 2, NPG Photo No. 1751 (APL))o On normal impact the Mk. 29-2 and flat-nosed limits were about equal but were 15# above the M79 limit. Since the differences in nose shape can account for only 2-336 at this e/d (references (1),(2) and (5)), these relatively high limits at normal obliquity must be attributed to the additional energy required to com- press the windshield. When the obliquity was increased to 30° and above the flat-nosed limits were decidedly lower than corresponding limits for the other projec- tiles. The rapid gain in efficiency of the flat-nosed projectile with initial increase in obliquity from normal is due to the deflection of the windshield out of the way with a lower loss of energy to the projec- tile than is required to compress the windshield at normal obliquity. For views of plate, projectiles and windshields see Figure 3 (NPG Photo No, 1658 (APL)), Figure 4 (NPG Photo No. I64O (APL)), Figure 5 (NPG Photo No. 1650 (APL)) and Figure 6 (NPG Photo No0 1651 (APL)).
At e/d of 0.36 the flat-nosed limits were below the M79 and Mk. 29-2 limits at obliquities from normal to 60°. (Figure 7 NPG Photo No, 1752 (APL))o From normal to 45° the flat-nosed limits were approxi- mately constant at 10% below the M79 limits and at 60° the limit was 80% of the M79 limit. The flat-
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FIGURE 10. NPÖ PHOTO NO. 1510 (APL). APL Plate No. 316 (Cam.-111. 275 Glass B No. 59533) vs. C.3.Co. 13-lb. flat- nosed projeotiles at 0° obliquity. FRONT VIEW. See NPG Photo No. 1511 (APL) for bade view and NPG Photos Nos. 1208-09, 1232-33 (APL) for previous impaots B.I.No. "e" "9" 3.V..f.3. Pane. % Proj.Cond. JJZnpL 2 7^30 0°j0' im ISST m aiaHered. Maroh 6, 1944 - CONFIDMTIAL -
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nosed limits decreased continuously relative to the M79 limits from about 85% at normal obliquity to 70% at 60°, Thus at this e/d over the full range of obliquities used the flat-nosed projectiles had limits from 10-30^ below those of the standard pro- jectiles.
At e/d of 0.49 the flat-nosed limits were consistently below the Mk. 29-2 limits but they fluctuated about the M79 values (Figure 8 NPG Photo No. 1753 (APL)). The flat-nosed limits increased from 75% at normal obliquity to 80-85% at 45°-60° obliquity with respect to the Mk. 29-2 limits. As compared with the M79 projectiles the flat-nosed projectiles had about a 10% advantage at 0° and 60° obliquity with a 10% disadvantage at 45° obliquity. The flat-nosed and M79 performances are essentially the same over the full range of obliquity at this e/d but both have a decided margin over the Mk. 29-2 projectile.
At e/d of 0.66 the flat-nosed projectile has lower limits than the Mk. 29-2 up to 45° but limits equal to or greater than the M79 projectiles (Figure 9, NPG Photo No. 1754 (APL)). The flat-nosed limits increased from 75% at normal obliquity to 95^ at 45° of the corresponding Mk. 29-2 values. The M79 and flat-nosed limits are approximately equal at 0° and 30° otliquities but at 45° the flat-nosed limit is 25% above the M79 limit. The high limits for the flat-nosed projectiles result from large projectile deformation.
At e/d of 0.81 and 0° obliquity the flat- nosed projectile was broken up with little penetration at a velocity slightly above the M79 limit. A view of the projectile and plate is given in Figure 10 (NPG Photo No. 1510 (APL)).
Against a divided armor structure consisting of 1/2" and 1" 3TS spaced 6 feet apart, all at 30° obliquity, the limit velocity for the flat-nosed pro- jectile was 67% of the Mk. 29-2 limit. This large difference in limits was a result not only of the difference in mechanism of armor penetration but also of the difference in yaw in the two cases. On every impact the Mk. 29-2 after penetration of the first plate (l^") acquired a yaw of about 45° before strik- ing the second plate. On the other hand the flat- nosed projectiles struck both plates at 0° yaw. One Mk, 29-2 projectile was broken up on impact with the second plate. (Figure 11, NPG Photo No. 1726 (APL)),
-5-
The limits for the present flat-nosed pro- jectiles are not as low as those reported for plain, unwindshielded flat-nosed projectiles in references (i; and (2) up to e/d of 0.5 (Suimnarized in Besults) but at the same time the limit velocities in general are 10^-25^ lower than are required by the best conven- tional projectiles. The lower limits for the earlier tests are accounted for by the lack of windshields and by the full-caliber flat nose (the diameters of the noses of the present projectiles were 0.92 caliber). However, the general behavior of the present projec- tiles as to type of plate failure and the remarkably low limits against thin plate at high obliquity and against divided structures are characteristic of all flat-nosed projectiles previously tested.
In the first tests of flat-nosed projectiles at the Naval Proving Ground (Reference (1))it was noted that projectile deformation In all cases Increased with increase of striking velocity. The same effects Zt™^}?0 ^oted ^ the Present tests. From the Appendix the following cases are cited. Against Vi75 STS at normal obliquity the increase In diameter of bourrelet ^ur2o0 f}°/sec< was 0'?020 and at 1150 ft./sec. it was 0i048. Against 2*0 STS at 30° the increase in diameter
0,.,G96 at 1^00 fto/sec.
Several rounds were fired at 1800-2000 ft./sec, to observe projectile deformation at high striking velocities. On this test some of the projectile noses were broken. At striking velocities of 1800-2000 ft./ sec. against T'STS the projectiles were broken at 0° and 45° but penetrated at 60° without appreciable deformation; against 1^5 STS they were broken at 0° and 60° but not at 45°; and against 2»J0 plate they were broken at 0° and 45°,,
From a consideration of the low limits observed for flat-nosed projerti] ,s against plates at e/d up to 0.5 and of the tencency to break up at higher velocities (.for the present projectiles 1800- 2000 f.s. arid above) it is evident that the flat-nosed principle is Ideally suited to service armor piercing rockets and bombs. For these projectiles have rela- tively low striking velocities"and are designed for the penetrating of lightly armored targets (e/d of 0.5 and below). Since the setback forces are low, light wind- shields can be used and thus keep their detrimental effects on penetration at a minimum. The application
—o —
of the flat-nosed form to common projectiles may be limited by the tendency to shatter at high velocity although the targets that can be successfully attacked are similar to those met by bombs and rockets. In the present war the Japanese Navy is known to have been using a type of flat-nosed common projectile of 8-inch caliber with which they have had a measure of success. (References (6) and (7)).
V.
1.
2.
VI.
CONCLUSIONS .3 3-inch 13.0 lb. flat-nosed projectiles fitted with windshields penetrate homogeneous plate at considerably lower velocities than do standard service projectiles over a wide range of test conditions including divided armor.
Although fl^t-nosed projectiles may pene- trate in an intact condition at low velocity, they may shatter under the same test condi- tions at high velocity. *
A REFERENCES x
1.
2.
3.
4.
5»
Penetration of Homogeneous Armor by 4-inch Flat-Nosed Projectiles» U.S. Naval Proving Ground Report No. 7-43 dated 19 April 1943<
Penetration of Homogeneous Plate Flat-Nosed Projectiles - Partial U.S. Naval Proving Ground Report dated 20 April 1944.
by 3-inch. Report //iJ NOo 12-44
-3!^
Penetration of Homogeneous Plate of One Tensile Strength (110,000 psi.) by 3" M79 AP Projectiles - Partial Report. U.S, Naval Proving Ground Report No. 8-44 dated Ah — 18 April 1944.
Penetration of Homogeneous Plate of One Tensile Strength (125,000 psi.) by 3" M79 AP Projectiles - Second Partial Report U.S. Naval Proving Ground Report No, 20-44 (In Preparation).
The Effect of Nose Shape on the Ballistic Performance of 15-lb. 3" AP Solid Shot Against Homogeneous Armor. U.S. Naval Proving Ground Report No. 2-43 dated 26 February 1943.
-7-
OC.U [\
6o Exa/nlnatlon of a Japanese 8-inch Common Projectile. U.s, Naval Proving Ground fleport No. 4-43 dated 12 March 1943,
7. UoS.S, SALT LAKE CITY (CA 25) Gunfire Damage, Bering 3ea 26 March 1943, U.S. Navy Bureau of ships Report No» 42 dated 15 May 1944. * * * **
VII, APPENDIX
BALLISTIC D^TA
Symbols
Vs(f.s.).... Striking velocity in feet per second.
VS W Striking velocity in per cent of standard value calculated from the Navy 1931 empirical formula:
F(e/d,0) - 6(e/d - 0.45j(ö2*2000)+40,000
where e and d are in the same units and e is the obliquity in degreeso The percentages in parenthesis after each experimental F(e/d,Ö) value are with respect to this empirical formula.
Pene (in,)... Depth of penetration in inches measured fro^i the front surface normal to the plane of the plate,
CP •• Complete penetration. Projectile com- pletely through and clear of the plate,
Inc 1*" Incomplete penetration - none of the projectile completely through and clear of the plate,
SIP Projectile stuck in plate. A special case of incomplete penetration,
Va (f.sj.... Residual velocity in feet per second of projectile after penetrating the plate.
:f
■
■
■
4 Increase in diameter in inches of the forward bourrelet of the projectile as a result of the impact,
v Projectile whole. The projectile may be deformed but because it is stuck in the plate measurements cannot be taken of the deformation.
D Projectile deformed,
E Projectile undeformed,
B(2).•♦.,.,. Projectile broken on a secondary impact.
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